1. Field of the Invention
The present invention relates to a switch circuit mainly used in high-frequency band wireless communications equipment, high-frequency band radar equipment, and the like.
2. Background Art
A switch circuit is used in the system for transmitting signals in a high-frequency band, such as a micro-wave band or a millimeter band. FIGS. 17, 18, and 19 are diagrams of systems using switch circuits.
In the system shown in FIG. 17, a switch SW is used for switching the transmitting and the receiving of signals. In the system shown in FIG. 18, a switch SW is used for switching signals from two antennas ANT. In the system shown in FIG. 19, a switch SW is used for preventing signals to be reflected from an antenna ANT and inputted into the receiver J1 when high-power signals are transmitted from the transmitter S1 in the system using a circulator CIR. Thereby, the receiver J1 containing a low noise amplifier can be protected. In these systems, a switch circuit using switching elements in series-parallel is used (for example, refer to FIG. 11 in Japanese Patent No. 4538016).